In European Patent No. 0,046,344 an art is disclosed of production of poly-.beta.-hydroxy butyrate (PHB) by the use of glucose. It is a technique of producing PHB by accumulating it in a cell by exhausting the source of nitrogen, making use of A. eutrophus NCIB 11599, which is a mutant strain of Alkaligenes eutrophus H16.
In European Patent No. 0,069,497 is disclosed a method of producing a copolymer of 3 HB (3-hydroxy butyrate) and 3HV (3-hydroxy valerate), which is the main constituent of PHB homo-polymer, by making use of organic acids such as propionic acid and glucose as carbon sources of A. eutrophus NCIB 11599. This copolymer is useful by changing the processability and various properties of PHB as well as lowering its degree of crystallization by the integration of 3HV elements in the molecular chain of PHB homopolymer.
In Japanese Patent Laid-open No. Sho 64-269989, Sho 64-48821, Hei 1-156320 are disclosed the methods producing several types of new copolymers in which 5HV (5-hydroxy valerate), 3HV (3-hydroxy valerate) and 4HB (4-hydroxy butyrate) are bonded together making use of A. eutrophus, with a view to the improvement of the mechanical properties of PHB.
In production of these improved copolymers, glucose and organic acids need to be used simultaneously, and in order to increase the contents of these copolymers it is required to increase the broth concentration of organic acids toxic to cells, whereby resulting in a remarkably lowered productivity of the copolymers, while the high price of glucose debases the economic advantages of this technique.
Again, European Patent No. 0,052,460 has disclosed the method of production of an improved PHB blend, with the view to the improvement of the mechanical properties of PHB, by means of blending PHB and non-biodegradable synthetic polymer, but this has a demerit in lowering bio-degradability of the blend which is the most important advantage of PHB indeed, because of containing the non-biodegradable synthetic polymer. Meanwhile Japanese Patent Laid-open No. Sho 63-226291 has disclosed a way of production of polyester copolymer making use of Pseudomonas oleovoran bacteria with saturated or unsaturated hydrocarbon (paraffin, olefin) as the carbon sources. This copolymer is a polymer from polyester bondings of 3-hydroxy carboxylic acids having 6 to 12 carbon atoms. Because of the poor contents of polyester accumulated and produced in the cells by restraining of nutrients, its productivity is extremely low.
In view of these, the development of a biodegradable polyester with lower degree of crystallization to help with the improvement of the properties of PHB is required, and so is the development of a process for raising the productivity of polyester with low degree of crystallization and yet biodegrable.
In J. Gen. Appl. Microbio, 1983, Vol. 29, pp 17-40, by Oyaizu et al it was made clear that various microorganisms of Pseudomonas genus have specificity in compositions of fatty acids and 3-hydroxy fatty acids in cells. According to Fulco's Prog. Lipid Res., 1983, Vol. 22, pp 133-160, 3-hydroxy fatty acids are widely distributed in most gram-negative bacteria; according to the biosynthetic process of PHA copolymer in oleovoran species. Introduced by Witholt et al in Appl. Environ. Microbiol., 1988, Vol. 54, No. 12 pp 2924-2932, 3-hydroxy fatty acids were polymerized by the action of acyl-CoA synthetase and PHA synthetase. These discoveries can mean that such PHA copolymers, composed of 3-hydroxy carboxylic acids having carbon atoms, ranging over C4-C16, can be produced by microorganisms.
For example, according to Biotechnology letters, 1989, Vol. 11, No. 7, pp 471-476, by Dawes et al, P. putida, P. oelovoran, P. aeroginosa, P. flourescence, and other species in Pseudomonas genus produce PHA polyester copolymer of 3-hydroxy acid with C6.about.C10 making use of alkane, alkanol, and alkanoic acids. But these bacteria do not use rapidly assimilated carbohydrates, such as glucose, fructose, sucrose in production of PHA, whereupon their productivity is low.